Zelda -> Pokemon = Mario
The Legend of Zelda series has not let me down so far: even the Oracle games, which are my least favourite, were enjoyable. The overall storyline, as well as the music, bosses, ect. all just seem to be excellent in every single game (The bosses moreso in the 3D- games, but even some of the 2D ones have their charm.).
Pokemon and Mario are tied on second place, but not even close to Zelda.
Mario, as it is the game I mainly grew up with.
Other: Fire Emblem.
I adore Mario, Zelda and Pokemon, but I'm a huge strategy and RPG fan and Fire Emblem appeals to me in so many ways.
Ex-Mod. Technically retired, they just won't let me quit.
I voted for Metroid only because Super Metroid is pretty much my favorite game ever
Now that being said, I think there are more Mario and Zelda games that are worth playing
But DAMN Super Metroid was a good fuckin game
“Alcohol may be man's worst enemy, but the bible says love your enemy." ~Frank Sinatra
Really tough choice, but I'm going with Legend of Zelda. Really fun story and I've always loved the medieval-style games.
EDIT: Oh hell, I forgot about Metroid. That goes above Zelda. Oh well.
I really like the wars series. I do love me some casual turn-based strategy.